1. Technical Field
The present invention relates to a method of capturing a satellite signal, or the like.
2. Related Art
As a positioning system using satellite signals, a GPS (Global Positioning System) is widely known, and is used for a position calculation device which is embedded in a mobile phone, a car navigation device, or the like. In the GPS, position calculation is performed to obtain the position coordinates and timepiece errors of the position calculation device on the basis of information regarding the positions of a plurality of GPS satellites or the pseudo distance from each GPS satellite to the position calculation device.
GPS satellite signals sent from the GPS satellites are modulated with spread codes which are called C/A (Coarse and Acquisition) codes and different between the GPS satellites. In order to capture the weak GPS satellite signals, the position calculation device performs correlation computation between the received signal (reception signal) of the C/A code and the signal (replica code) of a replica code simulating the C/A code to capture the GPS satellite signals.
Specifically, the correlation computation is performed while shifting the phase of the replica code, the phase at which the highest correlation value is obtained becomes a so-called code phase, and the GPS satellite signals are captured. For example, U.S. Unexamined Patent Application Publication No. 2006/0056497 discloses a technique for accelerating the acquisition of the GPS satellite signals in a weak electric field environment or the like.
However, in the correlation computation of the related art, processing for multiplying and integrating each of the sampling value of the reception signal and the sampling value of the replica code should be performed for the number of phase shifts. For this reason, the circuit scale inevitably increases. This problem causes an increase in power consumption.